1. Technical Field
The present invention relates to a light-emitting device, a method for manufacturing the light-emitting device, and an image display apparatus, and in particular, relates to a technology of solid-state light-emitting devices such as a light-emitting diode (hereinafter, referred to as an LED as appropriate).
2. Related Art
Projectors or image display apparatuses use, for example, a liquid-crystal spatial light modulator for modulating the light from a light source in response to an image signal. The liquid-crystal spatial light modulator modulates incident light by converting the state of polarization. With the liquid-crystal spatial light modulator, light from a light source can be used effectively by converting the light to polarized light vibrating in a specific direction. Techniques for supplying polarized light in a specific vibrating direction are proposed, for example, in JP-A-5-72417 and JP-A-2000-221499.
In an optical system including a light source and a spatial light modulator, spatial beam divergence can be expressed as the product of emission area and solid angle (etendue, geometrical extent). The spatial light modulator has limitation in the angle of light that can effectively be modulated (for example, within ±16° with respect to the optical axis. To make effective use of the light from the light source in the spatial light modulator, the etendue of the light source must be smaller than that of the spatial light modulator. JP-A-5-72417 proposes a technique of letting light of reduced width in a polarization conversion element. This technique can equalize the luminous flux width at the light-exiting surface of the polarization conversion element to the light source width, whereas it increases the etendue substantially double because the angle of incident light is doubled when the width of the luminous flux of the incident light is reduced.
Furthermore, in recent years it is proposed to use a solid-state light-emitting device as the light source of projectors. A light-emitting diode (hereinafter, referred to as an LED) which is a light-emitting element features microelement, ultralight, and long life. To use LEDs under development for projectors a plurality of LEDs must be used to provide light images. However, even if a lot of LEDs are used, it becomes difficult to make effective use of the light from the light source as the spatial divergence of light incident on the spatial light modulator increases. Accordingly, it is intended to reduce the etendue of the LEDs by controlling the angle of outgoing light with an optical device disposed directly at the light-emitting section of each LED.
With the structure shown in FIG. 1 of JP-A-2000-221499 in which an optical device is disposed at the light-emitting section, the light reflected by the reflective polarizer passes through the optical device and then returns to the light-emitting section. The eight incident on the optical device through the reflective polarizer for polarization conversion is dispersed by the optical device, thus making it difficult to reuse of the light efficiently. Thus, the related arts have problems in difficulty to decrease etendue and supply light at high polarization conversion efficiency.